Short‐cut method for the calculation of sterilization conditions yielding optimum quality retention for conduction‐type heating of packaged foods

Based on analytical equations for the temperature distribution history in a container, the relation between the reductions of the concentrations of heat labile food components, including microorganisms. nutrients and sensory factors, and the kinetic parameters of the reactions causing these reductions, has been calculated numerically. For a constant temperature of the heating medium with time it is concluded that the loss of quality is almost minimal at one Fourier value of the heating time. This optimal Fourier value is a function of only the Biot number and the relationship between initial product temperature, cooling water temperature and retort temperature. At an infinite value of Biot and a cooling water temperature equal to the initial product temperature the optimum Fourier value amounts to 0.5. On the basis of this conclusion a short‐cut calculation method is developed. The method is valid for Biot numbers larger than 10, initial homogeneous product temperatures equal to or larger than the temperature of the cooling medium and for the main container geometries including spheres, cylinders and rectangular bodies. The method does not require tedious interpolations of tables. The calculation of the optimum process conditions to obtain the desired sterility and the calculation of the retention of the quality factor of interest require only a few minutes on a pocket calculator. For routine calculations the procedure can conveniently be programmed